Blood substitutes in cardiac surgery

A safe, inexpensive, noninfectious substitute for red blood cells has long been sought. Despite tremendous advances in blood banking, the logistics of collecting, transporting, and storing human red blood cells continues to create infection and shortage problems. The two basic types of blood substitutes currently under development are hemoglobin based and fluorocarbon based. Although they each transport oxygen differently, the basic advantages and limitations are the same. Blood substitute advantages include the unique capacity for room temperature storage, noninfectively, adequate supply, and low toxicity. Restrictions include limited dosing in the acute period, limited intravascular half-life and, for the fluorocarbons, a requirement for a high PaO₂. In addition, there remain questions about the relationship of nitric oxide metabolism to hypertension in hemoglobin solutions. Early clinical and laboratory trials have shown that both types of solutions are effective oxygen-delivery agents, with acceptable side-effect profiles. Clinical trials are currently underway to determine the safety and efficacy of these solutions in patients undergoing cardiopulmonary bypass.